1. Field of the Invention
The present invention relates to a radiator assembly of the vehicle, particularly of a vehicle using the cooling water of a water cooled engine as a heat source for heating.
In a water cooled engine driven vehicle a radiator assembly is provided for heating purposes by supplying cooling water from the engine to a heat exchanger and heating passing air in the heat exchanger, and supplying the heated air into the compartment of the vehicle. The engine cooling water is used for heating because normally the heat capacity of the cooling water is very large and it normally is possible to obtain the needed and sufficient quantity of heat when the engine is operating. However, as the cooling water temperature remains low for a while particularly after starting the engine in a cold season, it then is not effective to use the cooling water of the engine for heating. In addition, in recently developed engines having high combustion efficiency the quantity of available heat outside the engine generally is relatively small. With such engines the temperature of the cooling water is hard to rise particularly after the engine start. It then is not suitable to use cooling water as a sole heat source for heating for a while after engine start. Conventionally the ability of heating in the warm-up phase after an engine start can be achieved by heating the cool cooling water in order to intentionally accelerate the temperature rise. This is carried out with the help of auxiliary heating equipment. FIG. 11 illustrates a cooling water circuit of a conventional radiator assembly of a vehicle. FIG. 12 shows the variations of the temperature of the conventional radiator assembly. An engine 101 having circulating pump 102 is connected with an inlet port of a thermal changeover valve 103. Said valve 103 has two outlet ports, one connected to an inlet of an engine radiator 104, another connected to a by-pass duct 105 by-passing the engine radiator 104. A junction part between the outlet of the engine radiator 104 and by-pass duct 105 is connected to an inlet port of the engine 101. Circulating pump 102 further is connected with an inlet of a three-ways 106, one outlet port of said valve 106 is connected via a by-pass duct 107 with the inlet port of engine 101. Another outlet port of valve 106 is connected to an inlet port of an auxiliary heat exchanger 108 which is provided with an auxiliary heater 109. The outlet of auxiliary heat exchanger 108 is connected to an inlet of a compartment heat exchanger 110, the outlet of which is connected to the inlet port of the engine 101. An example of such an auxiliary heating equipment having the auxiliary heat exchanger 108 and the auxiliary heater 109 is disclosed in JP patent application Hei 6-92134 (application number Hei 04-246294). The auxiliary heater used is a so-called shear exothermic equipment in which in shear forces act on a viscosity fluid by using the rotating power of the engine. The cooling water is heated by heat thus generated. Cooling water absorbs heat in engine 101 and is discharged by circulating pump 102 into thermal changeover valve 103. The respective passage is switched by said valve 103 according to water temperature. If the temperature is lower than a fixed temperature, valve 103 directs the flow into by-pass duct 105 and directly back into the engine 101. If the temperature is higher than said fixed temperature, valve 103 directs the flow into radiator 104, where the cooling water radiates heat and from where it returns into the engine 101. Another part of the cooling water from engine 101 reaches three-ways valve 106 operating according to the quantity of the heat needed by the compartment heat exchanger 101 and stabilising said quantity for the auxiliary heat exchanger 108 by directing the flow to the auxiliary heat exchanger 108 in case of high heating demand or by directing it to by-pass duct 107 in case of low heat demand. In auxiliary heat exchanger 108 the cooling water exchanges heat with air introduced from the outside of the vehicle or with air circulating in the vehicle via said compartment heat exchanger 110. The temperature then drops and the cooling water returns into the engine 101. When heating is needed and the temperature of the cooling water reaching compartment heat exchanger 110 is low, said auxiliary heater 109 is operated to heat the cooling water flowing into auxiliary heat exchanger 108. From there heated cooling water is supplied into said compartment heat exchanger 110. The temperature of the cooling water leaving engine 101 and entering auxiliary heat exchanger 108 is T1. The temperature of cooling water leaving auxiliary heat exchanger 108 towards compartment heat exchanger 110 is T2. The temperature downstream compartment heat exchanger 110 and in the return duct to engine 101 is T3. In the FIG. 12 the horizontal axis indicates the time after the engine start. The vertical axis indicates the temperature variations. During cruising with heating without operating auxiliary heater 109 the temperature of cooling water from engine 101 through auxiliary heat exchanger 108 into compartment heat exchanger 110 varies with curve 121; it rises gradually. The temperature T1 at the inlet of auxiliary heat exchanger 108 corresponds to temperature T2 (OFF) at the inlet of compartment heat exchanger 110. The outlet temperature T3 (OFF) after heat exchanging compartment heat exchanger 110 varies with curve 122. The difference between curves 121 and 122 represents the ability of heating available by compartment heat exchanger 110 without the assistance of auxiliary heater 109. The ability of heating is poor after engine start. By using auxiliary heater 109 the cooling water is heated in auxiliary heat exchanger 108. The temperature rises from T1 to T2 (ON) and varies with curve 123. Even though heating cooling water with temperature T2 (ON) exchanges heat in compartment heat exchanger 110, temperature T3 (ON) at the outlet will vary with curve 124. Therefore, the difference between curves 123 and 124 represent the heating ability of compartment heat exchanger 110 when the auxiliary heater 109 is operating. A shortage in the heating ability after engine start is supplemented. Further, the significant difference between curves 121 and 123 is effected by the operation of auxiliary heater 109. However, the efficiency of the auxiliary heater is poor.
Another example of an auxiliary heating equipment is discloses in DE-A-19752613. The auxiliary heating equipment of an automobile air conditioning system comprises an electric heater. Said electric heater consists of a NiCr-wire element provided within a section of the cooling water circuit. The efficiency of the electric heater is poor.